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Bioluminescence imaging (BLI) is a
technology Technology is the application of Conceptual model, conceptual knowledge to achieve practical goals, especially in a reproducible way. The word ''technology'' can also mean the products resulting from such efforts, including both tangible too ...
developed over the past decades (1990's and onward). that allows for the noninvasive study of ongoing
biological processes Biological processes are those processes that are necessary for an organism to live and that shape its capacities for interacting with its environment. Biological processes are made of many chemical reactions or other events that are involved in ...
Recently, bioluminescence tomography (BLT) has become possible and several systems have become commercially available. In 2011, PerkinElmer acquired one of the most popular lines of optical imaging systems with bioluminescence from Caliper Life Sciences.


Background

Bioluminescence Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorgani ...
is the process of light emission in living
organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
s. Bioluminescence imaging utilizes native light emission from one of several organisms which bioluminesce, also known as luciferase enzymes. The three main sources are the North American
firefly The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production ...
, the
sea pansy A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order sectio ...
(and related marine organisms), and bacteria like '' Photorhabdus luminescens'' and '' Vibrio fischeri''. The
DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
encoding the luminescent protein is incorporated into the laboratory animal either via a
viral vector A viral vector is a modified virus designed to gene delivery, deliver genetic material into cell (biology), cells. This process can be performed inside an organism or in cell culture. Viral vectors have widespread applications in basic research, ...
or by creating a transgenic animal. Rodent models of cancer spread can be studied through bioluminescence imaging, e.g. for mouse models of breast cancer metastasis. Systems derived from the three groups above differ in key ways: * Firefly luciferase requires D-luciferin to be injected into the subject prior to imaging. The peak emission wavelength is about 560 nm. Due to the attenuation of blue-green light in tissues, the red-shift (compared to the other systems) of this emission makes detection of firefly luciferase much more sensitive ''in vivo.'' * Renilla luciferase (from the
Sea pansy A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order sectio ...
) requires its substrate, coelenterazine, to be injected as well. As opposed to luciferin, coelenterazine has a lower bioavailability (likely due to MDR1 transporting it out of mammalian cells). Additionally, the peak emission wavelength is about 480 nm. * Bacterial luciferase has an advantage in that the ''lux''  
operon In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splic ...
used to express it also encodes the enzymes required for substrate biosynthesis. Although originally believed to be functional only in
prokaryotic A prokaryote (; less commonly spelled procaryote) is a single-celled organism whose cell lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Greek (), meaning 'before', and (), meaning 'nut' ...
organisms, where it is widely used for developing bioluminescent pathogens, it has been genetically engineered to work in mammalian expression systems as well. This luciferase reaction has a peak wavelength of about 490 nm. While the total amount of light emitted from bioluminescence is typically small and not detected by the human eye, an ultra-sensitive
CCD camera A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
can image bioluminescence from an external vantage point.


Applications

Common applications of BLI include ''in vivo'' studies of infection (with bioluminescent pathogens), cancer progression (using a bioluminescent cancer cell line), and reconstitution kinetics (using bioluminescent
stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...
s). Researchers at UT Southwestern Medical Center have shown that bioluminescence imaging can be used to determine the effectiveness of cancer drugs that choke off a tumor's blood supply. The technique requires luciferin to be added to the bloodstream, which carries it to cells throughout the body. When luciferin reaches cells that have been altered to carry the firefly gene, those cells emit light. The BLT inverse problem of 3D reconstruction of the distribution of bioluminescent molecules from data measured on the animal surface is inherently ill-posed. The first small animal study using BLT was conducted by researchers at the
University of Southern California The University of Southern California (USC, SC, or Southern Cal) is a Private university, private research university in Los Angeles, California, United States. Founded in 1880 by Robert M. Widney, it is the oldest private research university in ...
,
Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...
, USA in 2005. Following this development, many research groups in USA and China have built systems that enable BLT. Mustard plants have had the gene that makes fireflies' tails glow added to them so that the plants glow when touched. The effect lasts for an hour, but an utra-sensitive camera is needed to see the glow.


Autoluminograph

An ''autoluminograph'' is a
photograph A photograph (also known as a photo, or more generically referred to as an ''image'' or ''picture'') is an image created by light falling on a photosensitivity, photosensitive surface, usually photographic film or an electronic image sensor. Th ...
produced by placing a
light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...
emitting object directly on a piece of
film A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...
. A famous example is an autoluminograph published in ''Science'' magazine in 1986 of a glowing
transgenic A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...
tobacco plant bearing the luciferase gene of fireflies placed on Kodak Ektachrome 200 film.


Induced metabolic bioluminescence imaging

Induced metabolic bioluminescence imaging (imBI) is used to obtain a metabolic snapshot of biological tissues. Metabolites that may be quantified through imBI include glucose, lactate, pyruvate, ATP, glucose-6-phosphate, or D2-hydroxygluturate. imBI can be used to determine the lactate concentration of
tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s or to measure the metabolism of the brain.


References


Further reading

* * * {{DEFAULTSORT:Bioluminescence Imaging Photographic processes Bioluminescence Imaging